The complete genome sequence of an avian paramyxovirus serotype 1 (APMV-1) isolated from a black-headed gull (Larus ridibundus) in Sweden was determined and compared with other APMV-1 sequences. Sequence analyses showed that this isolate consists of six genes in the order 3'-NP-P-M-F-HN-L-5', is 15,186 nucleotides long, and contains a typical, avirulent fusion protein cleavage site. It was also shown to have a hemagglutinin-neuraminidase protein with a length of 585 amino acids (aa) instead of the expected 616 aa. Phylogenetic analyses showed that the isolate belongs to genotype I, and the relationship with some other, known APMV-1 virus sequences was revealed. Waterfowl have been considered to act as a reservoir for APMV-1 and, therefore, it is important to broaden the knowledge of viruses circulating within this population.